Transdermal Intraosseous Device

ABSTRACT

A transdermal intraosseous device includes a transdermal adapter for an external prosthetic device for a bone of a patient and a bone fixator including a distal portion coupled to the transdermal adapter and a proximal portion for anchoring into the bone. The transdermal adapter includes a dome-shaped portion for transcutaneous implantation and an external shaft extending from the dome-shaped portion. A dermal transition structure is configured to include a controlled roughness gradient from the external shaft to the dome-shaped portion and configured for use in infection control at a dermis layer of the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/016,766 filed on Jan. 28, 2011, which claims the benefit of U.S.Provisional Patent Application No. 61/300,277 filed on Feb. 1, 2010. Thedisclosures of the above applications are incorporated herein byreference.

INTRODUCTION

Various known external fixation devices for amputation or trauma includecompliant mechanisms for supporting a prosthetic device to a bone. Indevices of this type, the compliant fixation mechanism provides acompressive stress at the bone interface for preventing bone resorptionover time. Typically, a metal portion of the fixation device may extendbeyond the cut surface of the bone, such that soft tissue is attached tothe metal, rather than the bone.

The interface between the prosthetic device and soft tissue can be asource of infection. The present teachings provide devices and surfacetreatments associated with the transcutaneous portion of an externalprosthesis adapter.

SUMMARY

The present teachings provide a transdermal intraosseous device thatincludes a transdermal adapter for an external prosthetic device for abone of a patient and a bone fixator including a distal portion coupledto the transdermal adapter and a proximal portion for anchoring into thebone. The transdermal adapter includes a dome-shaped portion fortranscutaneous implantation and an external shaft extending from thedome-shaped portion. A dermal transition structure is configured toinclude a controlled roughness gradient from the external shaft to thedome-shaped portion and configured for use in infection control at adermis layer of the patient. The bone fixator can be a compliant bonefixator or a static, non-compliant bone fixator.

In some embodiments, the dermal transition structure includes a porousmetal dome-shaped structure surrounding and overlaying the dome-shapedportion of the transdermal adapter, and first and second transitionalsurface treatment layers between the external shaft and the porous metaldome-shaped structure along the longitudinal axis of the transdermaladapter. The first transitional surface treatment layer is roughened byblasting for contact with the dermis and the second transitional surfacetreatment layer is roughened by a combination of blasting treatment andacid-etching treatment for contact with the dermis.

The present teachings also disclose a method for providing a controlledroughness gradient transition between an external prosthetic device fora bone of a patient and the corresponding dermis of the patient. Themethod includes positioning a porous metal dome-shaped structure arounda metal dome-shaped portion of a transdermal adapter. An external shaftextends from the dome-shaped portion of the transdermal adapter and afirst portion of the external shaft is roughened by blasting. A secondportion of the external shaft is roughened by blasting and acid etching.The first portion extends above the porous metal dome-shaped structurealong a longitudinal axis of the external shaft and the second portionextends above the first portion along the longitudinal axis of theexternal shaft. The porous meal dome-shaped portion and the first andsecond portions of the external shaft are configured to contact thedermis for infection control.

Further areas of applicability of the present teachings will becomeapparent from the description provided hereinafter. It should beunderstood that the description and specific examples are intended forpurposes of illustration only and are not intended to limit the scope ofthe present teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1A is an environmental cross-sectional view of an exemplarytransdermal intraosseous device according to the present teachings;

FIG. 1B is an enlarged detail of FIG. 1A;

FIG. 2 is an isometric view of an exemplary transdermal intraosseousdevice according to the present teachings;

FIG. 3A is a plan view of a compliant fixator of the transdermalintraosseous device of FIG. 2;

FIG. 3B is a sectional view of the compliant fixator of FIG. 3A takenalong the line 3B-3B;

FIG. 4 is an exemplary anchor member of a transdermal intraosseousdevice according to the present teachings;

FIG. 5 is a sectional view of the compliant fixator of FIG. 3B shownassembled with the anchor member of FIG. 4;

FIGS. 6A-6C are various perspective views of a compliant fixator for anexemplary transdermal intraosseous device according to the presentteachings;

FIGS. 7A and 7B are perspective views of a transdermal adapter for anexemplary transdermal intraosseous device according to the presentteachings;

FIG. 8 is a perspective view of a patient-specific sleeve of anexemplary transdermal intraosseous device according to the presentteachings;

FIG. 9 is a perspective view of an exemplary quick release collar of atransdermal intraosseous device according to the present teachings;

FIG. 10 is a perspective view of an exemplary quick release lever of atransdermal intraosseous device according to the present teachings;

FIG. 11 is an exemplary output shaft of a transdermal intraosseousdevice according to the present teachings; and

FIG. 12 is an exemplary torque limiter of a transdermal intraosseousdevice according to the present teachings.

DESCRIPTION OF VARIOUS EMBODIMENTS

The following description is merely exemplary in nature and is in no wayintended to limit the present teachings, applications, or uses. Thepresent teachings can be used for attaching any external prostheticdevice to a bone through skin via a transdermal intraosseous device. Thetransdermal intraosseous device can include a transdermal adapter and anintraosseous fixator. In some embodiments, the intraosseous fixator canoptionally include a compliant fixator, such as, for example, theCompress® Pre-Stress Implant, which is commercially available fromBiomet, Inc. Warsaw, Ind., or a compliant fixator according to thepresent teachings and described herein. Compliance, as used herein, is ameasurement of softness as opposed to stiffness of a material.Compliance of a structural member is generally the reciprocal of Young'smodulus (one dimension) or the inverse of the stiffness matrix (morethan one dimensions). Accordingly, a compliant member is generally astructural member that has enhanced compliance, such as an elasticspring, bellows, Belleville washers and other elastically biasingmembers. The compliant fixator of the present teachings, as well as theCompress® Compliant Pre-Stress Implant, allows osseointegration at thebone/implant interface and can provide a stable, high-pressure/implantinterface. The compliant fixator can also assist in the prevention ofstress shielding and any concomitant bone loss.

Infection is generally a common complication with known transdermal(transcutaneous) intraosseous devices. Aggressive apical epithelialmigration, or epithelial downgrowth may be initiated as a normal woundhealing process to foreign bodies. If not prevented, this process mayresult in deep pocket formation and subsequent marsupialization of thetransdermal devices. In contrast, subepithelial connective tissueadhesion to a transdermal intraosseous device may prevent epithelialdowngrowth and associated complications, such as infection.

As discussed below, the transdermal intraosseous device of the presentteachings can include a transdermal adapter coupled to an intraosseousfixator, such as a compliant fixator or other intramedullary anchoringmember. The transdermal adapter can include a porous titanium material,such as Regenerex® Porous Titanium Construct, commercially availablefrom Biomet, Inc., Warsaw, Ind. Similarly to Regenerex®, the poroustitanium material may have an average porosity of about 67 percent andpore size ranging from about 100 to about 600 microns (average of 300microns), as well as high strength and flexibility

Referring to FIGS. 1A-7B, an exemplary transdermal intraosseous device10 according to the present teachings can include a transdermal adapter100 for connection to an external prosthetic device (not shown) and abone fixator 200 for compliant or non-compliant fixation into anintramedullary bore 84 of a bone 80, such as a femur, tibia, humerus,etc., that will receive the external prosthetic device. Accordingly, thebone fixator 200 can be a compliant fixator that can provide pre-stressto the bone or a non-compliant fixator in the form of a static(non-dynamic) anchoring member.

The bone fixator 200 can include a distal portion 202 and a proximalportion 204. The distal portion 202 is configured for coupling with thetransdermal adapter 100 outside the bone 80 in the subdermal soft tissue82 under the epidermis and dermis layers (skin) 86 of the patient, suchas, for example, with a taper connection, as discussed below. Theproximal portion 204 is received into the bore 84 of the bone 80 foranchoring into the bone 80 as discussed below. The bone fixator 200 canalso include an intermediate portion 206 between the distal portion 202and the proximal portion 204 of the bone fixator 200. The intermediateportion 206 can be a skirt-like collar and can be modularly or fixedlycoupled to the distal portion 202 and the proximal portion 204 and caninclude a porous titanium plasma spray 208 (FIG. 3A) with ahydroxyapatite (HAS) coating or other similar treatment for increasedbiologic fixation. The intermediate portion 206 can be fixed to aresected distal surface 88 of the bone 80 with anti-rotation pins orother fasteners 210 through corresponding apertures 212 at an anglerelative to a longitudinal axis A of the bone fixator 200, as shown inFIG. 3B. As shown in FIG. 1A, the longitudinal axis A is also a centeraxis of the transdermal adapter 100.

Referring to FIGS. 1A and 8, the transdermal intraosseous device 10 caninclude a centering sleeve 300. The centering sleeve 300 can include anouter surface 302 engageable with the bone bore 84 and an inner surface304 receiving and engaging the proximal portion 204 of the bone fixator200. In some embodiments, the centering sleeve 300 can bepatient-specific (customized for an individual patient). For example,the outer surface 302 of the centering sleeve 300 can bepatient-specific (customized for an individual patient) to conform tothe surface of the bone bore 84 based on a three-dimensional image ofthe bone bore 84. The a three-dimensional image of the bone bore 84 canbe generated via MRI, CT or other imaging methods of the patient'sanatomy during a pre-operative planning phase of the surgical procedureusing computer modeling technology commercially available, for example,by Materialise USA, Plymouth, Mich. Accordingly, the outer surface 302of the centering sleeve 300 can include, for example, patient-specific,cylindrical or piece-wise cylindrical, conical or other curved andclosed surface portions. The inner surface 304 of the centering sleeve300 can be configured to receive and engage the proximal portion 204 ofstandard (non-custom) bone fixators 200 of different standard sizes andcan be, for example, tapered, cylindrical, piece-wise cylindrical orpiece-wise tapered. In this regard, the centering sleeve 300 provides atransition from a patient-specific engagement with the bone 80 of thepatient to a standard engagement with one of the standard size bonefixators 200.

Referring to FIGS. 1A, 1B, 2, 7A and 7B, the transdermal adapter 100 caninclude a body 101 having a substantially dome-shaped portion 102received subcutaneously, and an external shaft 104. The body 101,including the dome-shaped portion 102 and the external shaft 104 can bemade as a monolithic (single) piece from a biocompatible metal, such aspolished titanium alloy (Ti-6-4). The dome-shaped portion 102 includesan internal bore or opening 105. The internal bore 105 can be taperedand receive a tapered distal portion 202 of the bone fixator 200 for ataper connection therebetween. In some embodiments, an extension 106 candepend proximally from the dome-shaped portion 102 toward the bone ofthe patient defining a circumferential slot or groove 108. A redundantconnector 350 can be used to provide an additional secured connectionbetween the intermediate portion 206 of the bone fixator 200 and theextension 106 of the transdermal adapter 100. The redundant connector350 can engage the groove 108 and can be, for example, a two-piece splitlocking nut or washer, as illustrated in FIG. 1A. The redundantconnector 350 can be tightened against the intermediate portion with aconnector element, such as a screw or other fastener (not shown) and canalso provide a tapered engagement with a corresponding tapered portionof the outer surface of the intermediate portion 206. Referring to FIGS.7B and 6B, a plurality of tabs 111 can protrude from the internal bore105 for engagement with corresponding slots 211 of the intermediateportion 206 of the bone fixator 200.

Regarding infection control, and referring to FIGS. 1A, 1B and 2, thetransdermal intraosseous device 10 of the present teachings can includea dermal transition structure 400 between the body 101 of thetransdermal adapter 100 and the dermis and epidermis 86 of the patient.The dermal transition structure 400 can include a porous metaldome-shaped structure 402 surrounding and overlaying on the dome-shapedportion 102 of the transdermal adapter 100. The material of the porousmetal dome-shaped structure 402 can be, for example, the Regenerex®Porous Titanium Construct discussed above. The porous metal dome-shapedstructure 402 can be attached to the dome-shaped structure 402 withlaser welding, brazing, sintering, or other methods.

The dermal transition structure 400 can also provide a controlledroughness gradient from the smooth/polished external shaft 104 to theporous metal dome-shaped structure 402. Accordingly, first and secondtransitional surface treatment layers 404, 406 can be included at theinterface between the transdermal adapter 100 and the dermis/epidermis86 for providing a roughness gradient. A first transitional surfacetreatment layer 404 is positioned and extends directly above the porousmetal dome-shaped structure 402 surrounding a contiguous portion of theexternal shaft 104 along the longitudinal axis A and contacting thedermis 86. The first transitional surface treatment layer 404 can be aroughness treatment on the external shaft 104 formed by blasting,including ceramic bead blasting, sand blasting, grit blasting andsimilar treatments.

The second transitional surface treatment layer 406 is contiguous to thefirst transitional surface treatment layer 404 and includes a blastingtreatment in combination with acid etching, such as anOsseotite®—treated surface. Osseotite® is a surface treatmentcommercially available from Biomet, Inc., Warsaw, Ind. Osseotite®treated surfaces may yield up to 110% increase in platelet adhesion andup to 54% increase in red blood cell (RBD) agglomeration over a smoothmachined surface. RBD agglomeration is known to enhance blood clotpermeability, which promotes wound healing. Increased platelet activitycan also lead to enhanced wound healing through the release of cytokinesand growth factors such as platelet derived growth factor (PDGF)-AB andtransforming growth factor (TGF)-beta1.

The dermal transition structure 400 provides a gradual transition fromthe polished outer surface of the external shaft 104 to the roughsurface of the porous metal dome-shaped structure 402 through the firstand second transitional surface treatment layers 404, 406. Thus, thefirst transitional surface treatment layer 402, has greater roughnessthan the second transitional surface treatment layer 404.

The dermal transition structure 400 may enhance dermal connective tissueadhesion, given that dermal tissue preferentially adheres to substrateswith percentage porosity and pore size similar to porosity of the porousmetal dome-shaped structure 402 and the Regenerex® material, asdescribed above. The roughness gradient from the porous metaldome-shaped structure 402 to the polished shaft 104 through the firstand second layers 404, 406 described above may provide dermal tissueingrowth as well epidermal adhesion, as described above.

As discussed above, the bone fixator 200 can be a compliant fixatorconfigured to provide a bone biasing force to a portion of a bone. Anyknown compliant fixator can be used, including, but not limited to, thecompliant fixators disclosed in commonly assigned U.S. Pat. Nos.7,141,073, 6,712,855, 6,508,841, 6,197,065, all of which are assigned tocommon assignee Biomet Manufacturing Corp., and are incorporated hereinby reference. The compliant fixator 200 is adapted to provide acompressive load on the bone, thereby reducing bone loss and promotingbone growth. The compliance of the bone fixator 200 can exceed that ofnative bone 80, such that stress shielding does not occur. Additionally,the native bone 80 can experiences physiologic dynamic compressiveloading biased by a preset spring compression. In this context, evidenceof bone hypertrophy or lack of bone loss may occur near the resectionlevel resulting in increased bone strength, possibly as a result of aphenomenon known as Wolf's Law.

Referring to FIGS. 3A-5, an exemplary compliant bone fixator 200 caninclude, for example, a compliant member 226. The compliant member 226can be include one or more compliant elements, such as one or moreBelleville washers, as shown in FIG. 3B or other spring washers or asingle or double helical spring. Detailed descriptions of the structureand operation of various compliant fixators 200 and biasing mechanismsare provided in the above-referenced patents. According to the presentteachings, the compliant member 226 ca be contained within alongitudinal bore 228 of the distal portion 202 of the bone fixator. Thelongitudinal bore 228 is shaped and configured for accommodating thecompliant member 226, such that the longitudinal bore 228 may have alarger diameter for Belleville washers than for a helical spring. Thecompliant bone fixator 200 can be anchored to the bone 80 andpre-stressed via an anchoring member 230. The anchoring member 230 caninclude an elongated shaft 232 attached to a plug 234 at a first end andhaving a threaded distal end 238. The plug 234, which can be enlargedrelative to the shaft 232, can include a plurality of apertures 236 forreceiving transverse bone fixation pins. The anchoring member 230 can beinserted through a longitudinal bore 224 that passes through the bonefixator 200 and through the Belleville washers when used as a compliantmember 226. The compliant member 226 can be held temporarily securedusing a removable tubular knob 220 having a bore 222. In this regard,the compliant bone fixator 200 can be inserted through a hole/incisionpunched through the skin and anchored into the bone 80 via the anchoringmember 230 while the compliant member 226 is held with the tubular knob220. A nut 240 can be threaded on to the distal threaded portion 238 ofthe shaft 232 and rotated to pre-stress the compliant member 226 to adesired amount. The knob 220 may then be removed. The transdermaladapter 100 can be impacted in position for locking the taperedconnection between the dome-shaped portion 102 of the transdermaladapter 100 and the distal portion 202 of the bone fixator 200. Thetransdermal adapter can also be locked with the redundant connector 350.The skin flap around the incision can be sutured around the externalshaft 104.

The compliant bone fixator 200 can be designed to have a fatiguestrength which is substantially greater than expected and/or estimatedloads transmitted from an external prosthetic device to the bone-implantinterface. Referring to FIGS. 1A and 12, as an added precaution, atorque limiter 530 can be installed in series with the exoprostheticdevice 10 to prevent a large torsional load transmission to thecompliant bone fixator 200 in the case of trauma or other unexpectedlyhigh load. The torque limiter 530 can be, for example, a two piecestepped device including first and second tubular shafts 534, 536 with acommon through bore 532 receiving a portion of the external shaft 104 ofthe body 101 of the transdermal adapter 100. The torque limiter 530 canbe, for example, a torque limiter commercially available from R+WAmerica, Bensenville, Illinois. The torque limiter 530 can be coupled tothe external shaft 104 with a quick release collar 500. An exemplarycollar 500 is illustrated in FIG. 9 and includes a central aperture 504and two end portions 506 defining a gap (slit in the collar). The collar500 can be locked and unlocked with an actuating mechanism, such as acammed lever 510. An exemplary cammed lever is illustrated in FIG. 10and includes a coupling end 512 and a curved engagement surface 514.

Referring to FIGS. 1A and 11, an exemplary output shaft 520 for theprosthetic device is illustrated. The output shaft 520 can include anotch 522 to control a failure mode and location in bending.

The foregoing discussion discloses and describes merely exemplaryarrangements of the present teachings. Furthermore, the mixing andmatching of features, elements and/or functions between variousembodiments is expressly contemplated herein, so that one of ordinaryskill in the art would appreciate from this disclosure that features,elements and/or functions of one embodiment may be incorporated intoanother embodiment as appropriate, unless described otherwise above.Moreover, many modifications may be made to adapt a particular situationor material to the present teachings without departing from theessential scope thereof. One skilled in the art will readily recognizefrom such discussion, and from the accompanying drawings and claims,that various changes, modifications and variations can be made thereinwithout departing from the spirit and scope of the present teachings.

What is claimed is:
 1. A method for forming a controlled roughnessgradient transition between an external prosthetic device for a bone ofa patient and the corresponding dermis of the patient, the methodcomprising: positioning a porous metal dome-shaped structure around ametal dome-shaped portion of a transdermal adapter; roughening a firstportion of an external shaft extending from the dome-shaped portion ofthe transdermal adapter by blasting to a first roughness, the firstportion extending above the porous metal dome-shaped structure along alongitudinal axis of the external shaft; and roughening a second portionof the external shaft by a combination of blasting and acid etching to asecond roughness, the second portion extending above the first portionalong the longitudinal axis of the external shaft, wherein the porousmetal dome-shaped portion and the first and second portions of theexternal shaft are configured to contact the dermis for infectioncontrol
 2. The method of claim 1, wherein the porous metal dome-shapedstructure has an average porosity of about 67 percent.
 3. The method ofclaim 261 wherein the porous metal dome-shaped structure has pore sizeranging from about 100 to about 600 microns.
 4. The method of claim 1,wherein the porous metal dome-shaped structure has average pore size ofabout 300 microns.
 5. The method of claim 1, wherein the first portionof the external shaft has a greater roughness than the second portion.